Expanded piston cup assembly



June 4, 1963 H. .1. SADLER ETAL 3,092,427

EXPANDED PISTON CUP ASSEMBLY 32 Filed May 8, 1961 4 I/VI/E/VTORS HARRY 1 54015;? m/vmr E. COOK A 7' TORNE y United States Patent 3,092,427 EXPANDED PISTON CUP ASSEMBLY Harry J. Sadler, Minneapolis, and Ernest E. Cook, Anoka,

Minn., assignors to Hypro Engineering, Inc., Minneapolis, Minn, a corporation of Minnesota Filed May 8, 1961, Ser. No. 108,526 6 Claims. (Cl. 309-51) as explained above, which is so constructed than an O-ring provides outward pressure at preselected areas of the assemblage such that a positive action is maintained in a reciprocating pump without appreciable increase in friction between piston and cylinder walls.

A further object of this invention is to provide a piston cup assemblage as set forth above which is inexpensive as to initial cost and to replacement repair cost.

In general, the resilient piston cup constructions of the conventional type available nowadays are adaptable for only one purpose. That is, several types are suitable for low drawing and low pressure pumping forces only. They utilize a reslient piston cup which has light sealing pressure on the cylinder side walls. There is also the type specially adapted for pumping high pressures from a low pressure or low vacuum inlet source, and these pistons also have a resilient cup construction but also have an appreciable and substantially fixed sealing pressure exerted against the cylinder side walls.

None of the above referred to pump pistons have a piston cup assemblage which is specially adapted for drawing fluids from a substantial vacuum or head of fluid and accordingly our invention does supply this much desired feature as will become evident subsequently.

These and other objects and advantages of our inven tion will more fully appear from the following description, made in connection with the accompanying drawing,

wherein like reference characters refer to the same or similar parts throughout the several views and in which:

FIGURE 1 is a top view of our special pressure washer;

FIGURE 2 is an assembly view in cross-section of the head end of our expanded piston cup assemblage;

FIGURE 3 is an enlarged cross-sectional view of the assembled piston cup assemblage, disposed within a cylinder, as it would appear during the pressure pumping stroke; and

FIGURE 4 is a similar view to that of FIGURE 3 but showing the relation of the piston elements during the drawing action.

Referring to FIGURE 1, we show the general configuration of a pressure washer which provides the novel results of our expanded piston cup assemblage. The pressure washer referred to generally as is annular in shape and has a concentric mounting hole 11 adapted for receiving a bolt as shown in FIGURE 2.

Referring to FIGURES 1 and 2, the pressure washer 10 is provided with a substantial thickness between the upper surface 1-2 and bottom surface 13 which is comparable to the open recessed portion 14 of annular piston cup 15. The side wall 16 of the pressure washer 10' has a recessed groove 17 which is annular with respect thereto. Seated within the groove 17 is a small distended and conventional O-ring 18 that is resiliently secured thereto.

3,092,427 Patented June 4, 1963 The annular cup 15 as shown, has an upper riding portion 19 which is continuous with a corner portion 20 and a base portion 21. The recessed portion 14 is formed by the inner side wall 22 and upper surface 23. The bottom base portion 21, having an upper surface 23, has an annular opening 24 for receiving the annular boss 25 of the backer 26. The outer surface 27 of riding portion 19 is slightly tapered inwardly as the surface 27 approaches the corner portion 20. The taper thereby causes a greater radially outward force at the upper end of the upper riding portion as will become apparent subsequently.

The backer 26 has a flange 28 which defines a recess 29 between the flange 28 and boss 25 for receiving the base portion 21 of the piston cup 15. The backer 26 also has a bore 30 for receiving the shank '31 of the bolt 32. Bolt 32 is threadably securable to an operating rod (not shown) and related means, such as bushing 32a, all of which form no part of the present invention.

In actual use of our expanded piston cup assemblage, the elements of FIGURE 2 would be assembled with their parts interfitting as seen in FIGURE 3. The O-ring 18 causes the inner side wall 22 to be forced outward a very slight amount and the O-ring is thus referred to as being in its relaxed position.

As may also be seen in FIGURE 3, the bolt shank 31 is journaled through the hacker bore 30 and engaged into elements not shown whereby to tighten the head 33 down upon the upper surface 1 2 of the pressure washer 10. By so tightening the bolt 32, the bottom surface 13 of the pressure washer 10 is gently forced against the boss 25 of backer 26 thereby causing no appreciable squashing pressure on the base portion 21 of the piston cup 15.

The assembling of the elements as shown, will cause the base portion 21 and corner portion 20 to seat in the recess 2? of the hacker 26 whereby the flange portion 28 of the backer will provide the necessary backing to the annular cup to prevent substantial deformity of the upper riding portion 19 during the operation of the piston.

As noted in FIGURE 3, the hacker 26 is of small enough diameter so that there is some amount of clearance 34 between it and the cylinder side wall 35.

The use and operation of our expanded piston cup assemblage will now be explained with reference to FIG- URES 3 and 4, however, it is to be noted that in actual practice the resilient piston cup actually does not separate from the frictional engagement with the cylinder side wall 35, as shown in FIGURE 4. The drawing indicates a separation since the functions of the 0-ring 18 and piston cup 15 have been over emphasized to more clearly explain and show the actions and reactions during the drawing portion of the pumping cycle.

During the pressure or exhaust stroke, the piston assemblage, while moving in the direction of the arrow as seen in FIGURE 3, would have the shown relation between components. That is, the O-ring issubstantia'lly undeformed in the relaxed position and the piston cup outer surface 27 is normally flexed with slight pressure against the inside surface of the cylinder wall 35 as explained above. During the pumping of a fluid in the cylinder chamber above the piston assemblage, the pressure built up would tend to aid the outward force of the piston cup thereby causing increased sealing properties, the amount of increased pressure depending upon the resilience of the piston cup material. This reaction will be readily understood by those skilled in the art.

Referring now to FIGURE 4, the piston assemblage is represented as traveling in the direction of the arrow or in the drawing or intake action of the pumping cycle. The elements of the piston cup assemblage are shown in their over emphasized acting and reacting relation as explained above. In this portion of the piston cycle there would be a tendency for the upper riding portion 19 of the piston cup todeform readily inward so as to allow fluid to pass from the area below the backer, betweenthe outer surface 27 and the side wall 35, and into the chamber area above the pressure washer and piston cup. At this point, the novelty of our invention becomes more readily apparent. As the drawing force is increased, the deformity of the piston cup 15- is increased, however, the O-ring 18 provides a soft cushion and reinforced backing to keep the side wall 22 of the piston cup urged outwardly and in frictional engagement with the side wall 35 at all times regardless of any reasonable drawing force. 'The 'O -ring is now shown deformed in the unrelaxed or reacting condition. Thus the conventional pumping characteristics of the piston cup during the pumping cycle are not substantially impaired as the drawing characteristics of the piston cup are substantially preserved even though increased drawing forces are required, for example, when a large head of water is encountered. I

By providing an O-ring as a resilient backing element to the inner side wall 22 of the piston cup, we have found that the resilient characteristic of the piston cup is still preserved during the drawing portion of the piston cycle whereas, had the backing material been of a rigid material, the important resilient qualities would have been substantially lessened.

An added advantage of our invention is that the O-ring, when worn out or otherwise rendered unsatisfactory for use, may be easily and economically replaced to again restore the pumping characteristics of the expanded piston cup assemblage when encountering high drawing forces.

It will, of course, be understood that various changes may be made in the form, details, arrangements and proportions of the parts without departing from the scope of our invention as set forth in the appended claims.

What is claimed is:

1. An expanded piston cup assemblage comprising, a resilient piston cup having an upper riding portion and a base defining a recessed portion with inner side walls, a relatively stiffer backer encircling said piston cup rearward ly of said upper riding portion and having an outer diameter no greater than that of said upper riding portion, a rigid means lying within the upper riding portion of said resilient piston cup, and. a distended biasing O-ring held outwardly by said rigid means in supporting relation against said inner side wall, whereby to maintain said upper riding portion in continual contact with the side wall of a cylinder, whereby said piston assemblage will cause substantial drawing forces as well as pressure forces during a pumping cycle. v

2. A combination comprising, a pump cylinder and an expanded piston cup assemblage having a conventional resilient annular piston cup, a backer for portions of said piston cup, a rigid means lying within said resilient piston cup, and an annular distended biasing O-ring encircling the edges of said rigid means and extending radially outwardly thereof for maintaining annular portions of said piston cup in continua-l contact with said pump cylinder when high drawing forces are encountered.

3. A combination comprising, a pump cylinder, and an expanded piston cup assemblage having a conventional resilient piston cup, a backer for portions of said piston cup, an annular pressure washer and an annular distended biasing O-ring encircling said pressure washer and extending radially outward thereof for exerting pressure on and maintaining annular portions of said piston cup in continual contact with said pump cylinder during a pumping cycle, said biasing means further exerting only slight biasing pressure during the exhaust stroke and exerting greater biasing pressure during the intake stroke, the biasing pressure increasing when drawing forces are encountered during the intake stroke.

4. An expanded piston cup assemblage comprising, a resilient body having a circular base portion and an annular upper riding portion joined thereto to define a recessed portion, said upper riding portion being tapered inwardly and rearwardly, a rigid backer held against said base portion in supporting relation thereto and having an outer diameter less than that of said upper riding portion, and a pressure washer disposed within said recessed portion having a distended resilient O-ring disposed between said pressure washer and said piston cup, whereby to maintain said upper riding portion in continual contact with a cylinder wall to prevent said upper riding portion from flexing radially inward when substantial drawing pressures are encountered during a pumping cycle.

5. An expanded piston cup assemblage comprising, a resilient annular piston cup having an annular upper riding portion adapted for frictional engagement with a cylinder side wall and a base portion, a backer engaging in supporting relation to said piston cup base portion, a

pressure washer disposed concentrically within said annular upper riding portion of said piston cup, said washer having an annular groove therearound, and a distended resilient toroid having portions seated in said annular groove and remaining portions extending outwardly thereof in interfitting contact between said pressure washer and said piston cup annular upper riding portion, whereby said toroid will provide a soft and resilient annular force to urge said annular upper riding portion outwardly for positive frictional engagement thereof with a cylinder side wall, whereby operation of said piston cup will not be substantially impaired when said piston encounters high. drawing forces.

6. An expanded piston cup assembly comprising, a resilient piston cup having an upper riding portion adapted to frictionally engage with the side walls of a fluid pump cylinder and abase portion secured to said upper riding portion, said base portion and upper riding portion defining a recess, said base further having an annular opening therethrough, a rigid backer having an upper surface held in abutting support to said piston cup, said backer also having a boss on the upper surface thereof for inter fitting in said piston cup annular opening, a pressure washer disposed within said recess of said piston cup and secured against said boss, and a distended resilient O-ring interfitted between said pressure washer and said upper riding portion, whereby to exert counteractant and increasing radially outward force upon said upper riding portion when said upper riding portion tends to deform radially inward due to increased drawing forces encountered during a pumping cycle.

Steedman Aug. 15, 1911 Foehr Feb. 6, 1934 

1. AN EXPANDED PISTON CUP ASSEMBLAGE COMPRISING, A RESILIENT PISTON CUP HAVING AN UPPER RIDING PORTION AND A BASE DEFINING A RECESSED PORTION WITH INNER SIDE WALLS, A RELATIVELY STIFFER BACKER ENCIRCLING SAID PISTON CUP REARWARDLY OF SAID UPPER RIDING PORTION AND HAVING AN OUTER DIAMETER NO GREATER THAN THAT OF SAID UPPER RIDING PORTION, A RIGID MEANS LYING WITHIN THE UPPER RIDING PORTION OF SAID RESILIENT PISTON CUP, AND A DISTENDED BIASING 